174 RESPONSE IN: THE LIVING AND NON-LIVING 
If there has been a feeble initial current, this 
oscillatory after-current, by algebraical summation, will 
cause the current in the circuit to be alternately weaker 
and stronger than the initial current. 
Visual recurrence.— Translated into the visual circuit, 
this would mean an alternating series of after-images, 
On the cessation of light of strong intensity and long 
duration, the immediate effect would be a negative re- 
bound, unlike the positive after-effect which followed 
on a short exposure. 
The next rebound is positive, giving rise to a sen- 
sation of brightness. This will go on in a recurrent 
series. 
If we look for some time at a very bright object, 
preferably with one eye, on closing the eye there is 
an immediate dark sensation followed by a sensation 
of light. These go on alternating and give rise to 
the phenomena of recurrent vision. With the eyes 
closed, the positive or luminous phases are the more 
prominent. 
This phenomenon may be observed in a somewhat 
different manner. After staring at a bright heht we 
may look towards a well-lighted wall. The dark phases 
will now become the more noticeable. 
If, however, we look towards a dimly leghted 
wall, both the dark and bright phases will be noticed 
alternately. 
The negative effect is usually explained as due to 
fatigue. That position of the retina affected by hght 
is supposed to be ‘tired,’ and a negative image to be 
formed in consequence of exhaustion. By this exhaus- 
